College not allowing switch from physics to biology

I’m in year 13 and had a change of heart over summer, wanting to drop physics and take biology instead; I’ve learnt the year 1 biology content over summer and was going to attend one of the mock retakes for the biology students, and if I did well I was going to ask to get moved to biology. My physics teacher has told me that even if I did well, this isn’t possible because of ‘college policy’. I don’t want to do physics for the rest of the year and find biology much easier and enjoy it more, and I don’t see why I shouldn’t be allowed to switch given that some people study an a level in a year, I could do well in the resit, and I could catch up with required practicals by sitting in for the year 12 classes if needed. Someone help me out, I feel like my physics teacher just doesn’t want me to drop physics

I would talk to the head of the college (or someone with a similar responsibility) to see what they say about it. How much did you communicate with your college about your intentions to do this?

I asked my physics teacher if it was possible and she flat out told me no; but I then asked the biology teacher if doing the retake was possible and she was open to it, and have the retake organised for next week, however my physics teacher pulled me aside during a lesson today and told me it is fully not possible because of college policy